The present invention relates to a method for bending difficult bending shapes such as an S-shape in a glass sheet, in which method:
a glass sheet is heated to a bending temperature PA1 the heated glass sheet is supported on an outline mould having a shaping surface which is complementary to a final bending shape, and PA1 the glass sheet is bent to its final configuration by pressing it from above and/or by supporting it from below by a non-engaging mould. PA1 an outline mould having a shaping surface which is complementary to a final bending shape, PA1 a non-engaging bending mould having a shaping surface which is complementary to a final bending shape.
The invention relates also to a bending mould assembly, comprising:
U.S. Pat. No. 4,260,409 discloses a method and an assembly for bending difficult bending shapes such as an S-shape in a glass sheet. A heated glass sheet carried on an outline mould is bent between upper and lower press shaping surfaces. The shaping surfaces are glass-engaging. Within the areas of difficult bending shapes a glass is locally elongated with a glass sheet being displaced between the shaping surfaces. This results in the abrasion of the glass surface. In any case, the engaging whole surface moulds leave marks on glass surface since a difficult shape cannot be obtained unless the glass is relatively soft (easily deformable).
An object of the invention is to provide an improved method and mould assembly for bending difficult shapes in a glass sheet in a manner that the bending can be effected in a controllable fashion also within the areas in which a glass sheet is subjected to intense elongation without creating adverse optical errors within these areas or in the immediate vicinity thereof.
This object is achieved by means of the invention on the basis of the characterizing features set forth in the annexed claims.